1. Field of the Invention
This invention relates to the production of alkali metal salts of oxy-substituted polycarboxylic acids, and more particularly to a method of preparation of alkali metal salts of oxyethylene dicarboxylic acids directly from the corresponding oxyethylene diols.
2. Prior Art
Caustic oxidation of aminoalkanols to the corresponding aminocarboxylic acid salts is known. See for example U.S. Pat. Nos. 3,535,373, 3,535,374, 3,535,375, and 3,842,081. Recently it has been disclosed in U.S. Pat. No. 3,717,676 that oxycarboxylic acid alkali metal salts can be prepared from the corresponding polyoxy-substituted primary alcohol and an alkali metal hydroxide in the presence of a cadmium catalyst.
It has now been discovered that alkali metal salts of oxyethylene dicarboxylic acids can be easily and effectively prepared by oxidizing the corresponding oxyethylene diol with an alkali metal hydroxide in the presence of a nickel-copper-chromia catalyst. Surprisingly, the process is very selective to oxyethylene diols. Monohydric oxy-substituted materials, such as butoxyethanol are not converted to the corresponding acid salt in accordance with the instant process.